Impact of Lead Acetate on Quantitative Consumption and Utilization of the Cotton Leaf Worm, Spodoptera littoralis (Boisduval, 1833) (Lepidoptera: Noctuidae)

The 3rd, 4th, 5th, and 6th instars of the cotton leaf worm Spodoptera littoralis (Boisduval, 1833) were treated with lead acetate, 100 mg lead [Pb (C2H3O2)4]/kg, using the leaf-dip method, to evaluate the effect of Pb on nutritional indices. The consumption index was significantly increased at the 3rd and 6th instars. The growth rate significantly increased in 4th instars. The reverse was true in 6th instars. The absorptive capacity, in terms of approximate digestibility, was insignificantly changed in the entire instars. The food utilization efficiencies, in terms of the conversion of ingested (ECI) and digested food (ECD) to biomass, were significantly increased in 4th instars. However, the ECD was significantly decreased in the 5th and 6th instars. In conclusion, treatment with lead may adversely affect the population biomass of S. littoralis due to the gross reduction in the final weight gain of larvae approaching to pupation. This might lead to reduced level of population size.